This paper is concerned with the heterogeneous networks (HetNets) in which a macro base station (MBS) serves one macro-user (MU) while a femto base station (FBS) communicates with multiple femto users (FUs). All terminals are equipped with multiple antennas and share the common frequency band. The signal transmission in such HetNets suffers both intra-tier and cross-tier interference. This paper will introduce downlink transmission strategies of the MBS and FBS to eliminate all interference and maximize the system channel capacity. Particularly, the MBS deploys the eigenmode transmission while the FBS aligns its signals into the unused eigenmodes of the MBS transmission. In addition, interference at the FUs is cancelled by aligning the interference signals into the null space of the proper interference channels. Finally, the precoders at the FBS are designed to maximize the total sum rate by an efficient convex optimization algorithm. The numerical experiments are provided to evaluate the sum rate performance of our method in comparison with the other existing approaches.